The Spanish were a tiny fraction of their own fighting forces. Their victory was a political achievement, leveraging deep-seated resentments of subjugated peoples against the Aztec and Inca empires, turning local populations into the primary military asset.

Despite commanding armies of tens of thousands, Inca generals were so disoriented by the unheard-of capture of their divine emperor that they offered no resistance. This complete bewilderment allowed a handful of Spaniards to dictate terms to a vastly superior force.

The Spanish didn't defeat the Inca Empire at its height. They arrived after a smallpox epidemic killed the emperor and a subsequent brutal civil war between his sons shattered the empire. This left the civilization politically fractured and militarily exhausted, making it ripe for conquest by a small force.

The absolute divine authority of the Sapa Inca meant that capturing a single man, Atahualpa, effectively paralyzed a 12-million-person empire. With no alternative power structure, his generals were bewildered and leaderless, allowing a tiny Spanish force to maintain control.

The Aztec military doctrine and status system prioritized capturing enemies alive for ritual sacrifice. This cultural imperative repeatedly led them to try to seize Cortés and other Spaniards rather than kill them on the spot, providing crucial moments for the conquistadors to be rescued and escape certain death.

After executing Inca emperor Atahualpa, the Spanish installed his brother as a puppet ruler. This co-opted the existing power structure, making the conquest seem like a restoration of the natural order to local chiefs and smoothing the transition of power.

The narrative of a small Spanish force conquering a vast empire is misleading. The Spanish heavily relied on indigenous allies, like the puppet emperor Paolo Inca, who provided thousands of warriors. These alliances were decisive in key battles, revealing the conquest was also a native civil war exploited by Europeans.

The Spanish conquest of the Incas succeeded largely because they inserted themselves into an existing civil war. By siding with the southern Inca faction against the northern one, they gained crucial local allies, transforming the conflict from a foreign invasion into a complex, multi-sided war they could manipulate.

Francisco Pizarro's invasion of Peru was heavily influenced by the recent success of his cousin, Hernán Cortés, in Mexico. The fall of the Aztecs provided a tangible model for conquest, proving that small bands of conquistadors could topple vast empires. This precedent made it easier for Pizarro to secure funding and royal support.